Bump kotlin from 1.7.0 to 2.0.21

Bumps `kotlin` from 1.7.0 to 2.0.21.

Updates `org.jetbrains.kotlin:kotlin-stdlib` from 1.7.0 to 2.0.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.0.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.7.0...v2.0.21)

Updates `org.jetbrains.kotlin.jvm` from 1.7.0 to 2.0.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.0.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.7.0...v2.0.21)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-stdlib
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.jetbrains.kotlin.jvm
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

gradle/libs.versions.toml

@@ -3,7 +3,7 @@
 reactorCore = "3.5.20"
 reactorAddons = "3.5.3-SNAPSHOT"
 # Other shared versions
-kotlin = "1.7.0"
+kotlin = "2.0.21"
 
 [libraries]
 reactor-core = { module = "io.projectreactor:reactor-core", version.ref = "reactorCore" }